The present invention relates to a magnetic head for multi-track magnetic recording operation, having arrays of read and write transducer elements formed by thin-film photolithography technology.
In recent years, there has arisen an increasing demand for increased speed of data transfer to and from various types of magnetic recording apparatus, particularly in the case of high-density tape recording apparatus. For this reason, multi-track recording has been adopted whereby a substantial number of read and write transducer elements for respective recording tracks are used to configure a magnetic head. Due to the extremely small spacings between the read and write transducer elements of respective tracks, and the extremely small sizes of the transducer elements themselves, it has become uneconomical to employ conventional manufacturing techniques to form the individual transducer elements (e.g. by winding individual coils for each transducer element, using wire) and hence thin-film techniques have been adopted to manufacture such a magnetic head. With such a method, a large number of thin-film transducer elements can be formed on a substrate formed of a magnetic material such as ferrite, using photolithography techniques. It is necessary to utilize respectively different configurations for the read and the write elements of such a magnetic head.
With such a thin-film magnetic head, each of the write transducer elements is manufactured by forming a thin-film coil upon a substrate consisting of a suitable magnetic material, which functions as respective magnetic cores for these transducer elements. Another magnetic substrate may be placed directly over this thin-film coil, to function as upper magnetic cores for the transducer elements. Alternatively, a film of electrically insulating material may be formed over the thin-film coil, and a thin film of a metallic magnetic material is then formed over this insulating film, to constitute the upper magnetic cores.
A magnetoresistive element (formed from a metallic magnetic thin film which exhibits magnetoresistive properties) is used to constitute each of the read transducer elements of such a thin-film magnetic head. Such a read element is typically manufactured by first forming a thin electrically insulating film upon a substrate of magnetic material, then forming a permalloy thin-film (which exhibits magnetoresistive properties) over this insulating film, to a thickness of typically 500 angstroms. An electrically insulating thin film is then formed over the permalloy film, and finally a substrate formed of magnetic material is placed in contact with the latter insulating film In some cases, an electrically conductive layer is formed below the aforementioned permalloy film, for use in producing a biasing magnetic field. This is done in order to increase the linearity of read signal generation by such a read transducer element.
A prior art example of such a thin-film magnetic head, for use in a multi-track magnetic tape recording apparatus, has been described in I.B.M. J. Res. Develop. Vol. 30, No. 3, pages 270 to 276. As described in that article, thin-film write transducer elements are formed on one substrate, while thin-film read transducer elements are formed on another substrate, to form respective thin-film read and write heads, i.e. respective modules one of which is formed only with read elements and the other formed only with write elements. These modules are combined to form the final magnetic head. However with one method of data recording utilized for such multi-track tape recorders, called "read-after-write" operation, data written on each tape track are read out immediately after being written, in order to check for write errors. In addition, a capability for bi-directional operation of such a tape recording apparatus is desirable, i.e. it should be possible to execute writing of data both when the tape is moving in a forward direction and when the tape is moving in the reverse direction. This is not possible by using a combination of a thin-film read magnetic head and a thin-film write magnetic head according to the prior art of the type described in the aforementioned I.B.M. article, since data writing will be only possible for one direction of tape movement, if "read-after-write" operation is to be executed. In order to implement such "read-after-write" operation with thin-film head modules of the type described, it would be necessary to use a combination of three such modules, i.e. a combination of a write head, a read head and a write head successively arranged in that order, such that each tape track moves past a write thin-film transducer element, a read transducer element, and a write transducer element, for each direction of movement of the tape. Alternatively, a combination of a read head, a write head and a read head successively arranged in that order could be utilized. However if either of these arrangements is used, it becomes difficult to ensure that the tape will be maintained in stable contact with each of the three thin-film head modules. Thus, such a prior art magnetic head has the disadvantage that stable recording and playback operation is difficult to achieve.